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Life Cycle of Tuna
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Life Cycle of Tuna
By Christina Kohlbeck and Kayla Criddle
Life Cycle
Fertilization
Tuna use external fertilization with the broadcast spawning method. Females release their eggs into the water and males release their sperm to fertilize them as they float to the surface.
Eggs
Eggs are spawned over the ground area of ocean water. After hatching, the eggs float to the surface where they live in planktonic surface waters.
Eggs
Parental Care and Gestation
Two day gestation period. After being hatched eggs/larvae are not cared for by the parents.
Parental Care & Gestation
Planktonic larvae
After hatching, larvae float up to the planktonic surface waters, where they feed on all other larval species.
Planktonic Larvae
Stages of the Life Cycle
Fertilization - spawning ground area of ocean floor. lasts 2-4 days
Larval stage - planktonic zone of spawning ground. lasts 6 months.
Juvenile - spawning grounds and open ocean feeding grounds. lasts around 5 years
Adult - open ocean feeding grounds. lasts 5-25 years depending on the species.
Advantages - allows many males and females to be in close proximity
Fertilization
Features - many unfertilized eggs are lost so females lay millions each year
Advantages - rich feeding area, not in competition with the adults
Larval Stage
Features - larvae have large heads and mouth parts to obtain food
Advantages - move in shoals of similar size to evade predators, have different and larger food than larvae
Juvenile
Features - juveniles leave the spawning grounds in shoals and roam the ocean feeding. very high growth rate
Advantages - rich diversity of food, not in competition with larvae
Adult
Features - adults migrate to the spawning grounds where they themselves were spawned during breeding season
Geographical Range
Geographical Range
Aquaculture
Bluefin tuna aquaculture is the most common. It is not technically aquaculture, it relies on obtaining wild juvenile tuna. It is referred to as ranching.
Aquaculture and Human Impact
Use pure seine nets to get the juvenile fish. Tow boats then tow the fish in cages to reduce damage. The fish are then transferred to tanks where they live for up to 8 months.
Can be damaging to the environment because they are juveniles, so they don't have the chance to reproduce. Also the pure seine nets can catch other species and potentially kill them in the nets.